Here are some key aspects of the experience that make it supernatural:
* The raven's arrival: The raven enters the speaker's room through a window, seemingly out of nowhere, on a stormy night.
* The raven's ability to speak: The raven is not just any ordinary bird. It speaks to the speaker in a human voice, answering his questions with the single word "Nevermore."
* The raven's knowledge: The raven appears to know about the speaker's grief and loss, as its "Nevermore" answers repeatedly evoke the speaker's lost love, Lenore.
* The raven's ominous presence: The raven's presence is unsettling for the speaker. The bird's black plumage, its gleaming eyes, and its constant repetition of "Nevermore" contribute to a growing sense of dread and despair in the speaker.
* The raven's mysterious nature: The poem never fully explains the raven's origin or purpose. It remains a mysterious, haunting presence that symbolizes the speaker's despair and the inevitability of death.
This supernatural experience is central to the poem, as it triggers the speaker's descent into madness and despair. The raven, with its ominous pronouncements and uncanny knowledge, becomes a symbol of the speaker's own inner demons and his inability to escape the grip of grief.